The field of the invention is water valves and the invention relates more particularly to valves used at the base of a gridded sprinkler system.
Sprinkler systems are commonly used in commercial buildings to provide an automatic water spray in the event of a fire which automatic spray can, and often does, prevent a fire from spreading. When the commercial building is a relatively large building, the amount of water captured in the fire sprinkler system is substantial. The water pipes must be sized to permit a substantial flow of water in the event of the opening of one or more sprinkler heads. It is also necessary that one or more check valves be provided to prevent the water in the system from re-entering the city water supply. The result is a substantial volume of water within a closed piping system. When the temperature of this water in the closed piping system increases slightly as the surrounding area warms, some method must be provided to permit the water to escape. If this is not done, a serious leak or damage to the system might result. Thus, it is common to provide a pressure relief valve at the base of the system to relieve such excess pressure.
However, the simple placement of a pressure relief system at the base is not sufficient because the system also must permit two types of testing. One type of testing is provided to test the alarm system. This alarm test is meant to simulate the flow of water from a sprinkler in the event of a fire which flow is intended to sound an audible and often to trigger other alarms such as an automatic dialing alarm. A further test is also required which is a pressure test where the system must be permitted to be brought to a relatively high pressure such as at least 200 psi for two hours.
To accomplish this combination of requirements, a "Christmas tree" of fittings is typically used which includes two tees, two on/off valves, a pressure relief valve and a loop of piping to provide two separate flow paths.